Tyrosine-capped gold nanoparticles enhance AamAP1-Lys-NH2 antipseudomonal efficacy in burn wound infection model

Effective management of infected skin wounds, particularly those complicated by Pseudomonas aeruginosa and rising antibiotic resistance, remains a major clinical challenge. Antimicrobial peptides (AMPs) offer strong potential to combat multidrug-resistant pathogens, but their clinical translation is severely hampered by poor stability in protease-rich physiological environments and inherent cytotoxicity that can impede wound healing. Current conjugation methods for loading AMPs onto nanoparticles often suffer from low peptide loading or require specific cysteine residues, limiting their broad applicability and therapeutic potential.

Researchers developed a robust method for loading the AMP, AamAP1-Lys-NH2, onto tyrosine-capped gold nanoparticles (Tyr-AuNPs) without requiring cysteine residues or linker molecules. Peptide loading was confirmed using Fourier-transform infrared (FTIR) spectroscopy and confocal microscopy. They assessed AMP release kinetics in water and PBS. In vivo efficacy was evaluated in a Galleria mellonella larvae model of P. aeruginosa burn wound infection, comparing AamAP1-Lys-NH2-AuNPs and its all-D-enantiomer against free AMP. Larval survival served as the primary endpoint.

The Tyr-AuNP platform achieved nearly complete peptide loading of AamAP1-Lys-NH2, significantly reducing cytotoxicity and conferring resistance to trypsin degradation. Cumulative release studies demonstrated gradual aggregate dissociation with slow AMP release in water (20% after 1 hour), while showing faster, complete release in PBS (100% after 1 hour), indicating potential for tuneable delivery. This suggests the AuNP formulation can protect the peptide until it reaches the target environment. Both the L-enantiomer AamAP1-Lys-NH2-AuNPs and its all-D-enantiomer performed equally well in vivo.

In the Galleria mellonella larvae model, AuNP-loaded AMPs significantly improved survival against P. aeruginosa burn wound infections to 80-85%, a substantial increase compared to 55% survival observed with free AMP alone. This equal performance of both enantiomers suggests that the additional costs associated with D-enantiomer synthesis are unwarranted when utilizing AuNP delivery, simplifying future development.